Photoelectric measurement

Terahertz vector measurement system based on AlGaN/GaN HEMT terahertz mixer
Liu Yiting, Ding Qingfeng, Feng Wei, Zhu Yifan, Qin Hua, Sun Jiandong, Cheng Kai
2023, 52(1): 20220278. doi: 10.3788/IRLA20220278
[Abstract](37) [FullText HTML] (12) [PDF 2448KB](18)
Vector measurement is an important technology for beam testing of antennas and quasi-optical systems in terahertz band. This paper introduces a terahertz vector measurement system based on a high-sensitivity AlGaN/GaN high-electron-mobility transistor (HEMT) terahertz detector integrated with a quasi-optical lens and waveguide together, which reached the noise equivalent power of −113 dBm/Hz in heterodyne mode at 340 GHz. A hardware circuit is established based on the double frequency-down-conversion technique to suppress phase noise in the system. The experimental results indicate that the minimum measurable power is 119 nW and the phase stability is better than 4° of the system. Measurement of the distribution of both terahertz amplitude and phase has been achieved based on this coherent AlGaN/GaN HEMT detector. An arrayed terahertz vector measurement system could be developed based on this work.
Diffuse reflection characteristics measurement of new type spaceborne solar calibration diffuser in ultraviolet band
Zeng Jiexiong, Huang Yu, Li Zhanfeng, Lin Guanyu, Li Yuan
2023, 52(1): 20220339. doi: 10.3788/IRLA20220339
[Abstract](28) [FullText HTML] (7) [PDF 2507KB](15)
The Lambertian diffuse reflectance characteristics of the spaceborne solar calibration diffuser and its radiation attenuation characteristics directly determine the long-term accuracy and stability of the on-orbit radiation calibration of space remote sensing instruments. In order to effectively improve the on-orbit radiation calibration accuracy of spaceborne ultraviolet hyperspectral detection instruments, based on the introduction of commonly used solar calibration diffuse reflector materials in the field of space remote sensing, a new type of ultraviolet wavelength diffuser material is proposed: high purity opaque fused silica material HOD, and the diffuse reflection Lambertian characteristics and radiation attenuation characteristics of the new high purity opaque Fused silica HOD diffuser and the traditional aluminum diffuser are compared by testing. The results show that after 32 equivalent solar hours (32ESH) of vacuum ultraviolet irradiation, the attenuation of the high purity opaque Fused silica HOD diffuser at the wavelength of 290 nm is 7.5%, which is better than 10% of the traditional aluminum diffuser. And the Lambertian maximum cosine deviation of the traditional aluminum diffuser around 290 nm is about 40%, while the high purity opaque Fused silica HOD diffuser is about 10%. Therefore, the diffuse reflection characteristics of the new high purity opaque Fused silica HOD diffuse reflector in the ultraviolet band are better than those of the traditional aluminum diffuser. The high purity opaque Fused silica hod diffuser has better diffuse reflection Lambertian characteristics and stronger vacuum ultraviolet radiation attenuation characteristics, so it can improve the long-term accuracy of the on-orbit radiometric calibration of space ultraviolet remote sensing instruments.
Two-position initial alignment method for redundant rotating inertial navigation system
Zou Tao, Wang Lifen, Ren Yuan, Zhu Ting
2023, 52(1): 20220414. doi: 10.3788/IRLA20220414
[Abstract](18) [FullText HTML] (7) [PDF 1708KB](16)
Redundant Rotating Inertial Navigation System (RRINS) can further improve the reliability of the system on the basis of traditional rotating inertial navigation system. Aiming at the high-precision initial alignment requirements of this type of system, A two-position initial alignment method was studied by taking the regular tetrahedral redundant rotating inertial navigation system as an example. Firstly, every three gyroscopes and three accelerometers constituted a combination. The zero bias correlation and redundancy configuration of the inertial device under each combination were established. And the RRINS two-position stop scheme was designed to estimate the zero bias of the corresponding inertial device. But in some special cases, the observation position needs to be increased. Then, the results obtained by each inertial device under different combinations were averaged, and the average value was used to compensate the measurement information of the corresponding inertial device. Finally, based on the compensated inertial device output performs the initial alignment of the RRINS. Mathematical simulation and experimental verification results show that the method can effectively estimate the zero bias of the inertial device under different two-position schemes. In the simulation, the bias estimation error of the gyroscope is within 4%, and the bias estimation error of the accelerometer is basically within 2%. Compared with the case without bias compensation, the initial alignment accuracy is improved by more than 10 times. In the experiment, the initial alignment accuracy in both horizontal and azimuth directions was improved, and the heading angle alignment error was reduced by about 100 times. At the same time, the method can also be extended to redundant rotating inertial navigation systems with other configuration schemes, which has certain reference significance for improving the initial alignment accuracy of such inertial navigation systems.
Research on rotating splicing of point cloud in workpiece wall based on surface structured light
Liu Jinyue, Zhai Zhiguo, Jia Xiaohui, Xue Luming, Li Tiejun
2022, 51(9): 20210952. doi: 10.3788/IRLA20210952
[Abstract](57) [FullText HTML] (10) [PDF 1564KB](32)
In order to solve the problem of limited internal space and difficult measurement of some workpiece, a point cloud rotating splicing method based on surface structured light was proposed. The reconstruction method of single field of surface structured light was introduced in this paper. The absolute phase value was obtained by combining four-step phase shift and complementary Gray code, and the camera and projector were calibrated by polynomial fitting method. The point cloud registration was studied based on the rotation plane of the wrist joint at the end of the manipulator. A calibration method based on the auxiliary camera was proposed, and the transformation relationship between the camera imaging coordinate system and the rotation plane coordinate system was given. The experimental results show that the method is suitable for measuring the inner wall of workpiece, and the average error of splicing is less than 0.05 mm, which meets the requirements of practical application.
Research on optical scattering characteristics of targets based on single photon detection
Li Zhiting, Liu Changming, Wang Yuye, Chang Jiying, Chen Kai, Li Jining, Zhong Kai, Xu Degang, Yao Jianquan
2022, 51(9): 20210825. doi: 10.3788/IRLA20210825
[Abstract](102) [FullText HTML] (16) [PDF 1764KB](49)
The single photon scattering echo characteristics of targets were studied in this paper. An optical scattering characteristic measurement system was built based on infrared single photon detector and picosecond laser. The number of echo photons was used to characterize the optical scattering characteristics under the condition of single photon detection. In this experiment, the single photon scattering characteristics of targets with different shapes (sphere, cube, cylinder and cone) were studied. And the results were fitted by using the bidirectional reflection distribution function model. The experimental results were in good agreement with the theoretical fitting ones. Further, the single photon scattering characteristics of targets with different materials (ceramic tile, wood and wall brick) were studied, which were compared with the traditional wave scattering characteristics. This study provides a reference for the long-range target recognition and detection of single photon lidar.
Calibration method of quad-camera measurement system based on tensor decompose
Li Yunhui, An Dongyang, Miao Zhonghua
2022, 51(9): 20220103. doi: 10.3788/IRLA20220103
[Abstract](56) [FullText HTML] (20) [PDF 2969KB](36)
Camera calibration is essential for vision measurement. In order to realize the accurate calibration of the multi-camera measurement system, the existing multi-camera calibration methods based on 1D (one-dimensional) targets are analyzed, and a multi-camera calibration method based on tensor decomposition is proposed. The method includes three aspects: (1) A mathematical model of multi-camera calibration is established with pin-hole model and rigid body transformation theory; (2) A problem of multi-camera calibration approach based on the fundamental matrix is analyzed, which is the calibration results coupled with each other; (3) In order to address this problem, the quad-focal tensor of a quad-camera measurement system is introduced to the calibration process, which includes that the quad-tensor is solved by using the image point of 1D calibration objects, and a reduced method for the quad-focal tensor is used to refine the camera matrices. Finally, the effectiveness and accuracy of the method are verified by experiments. The results indicate that (1) The calibration of the quad-camera 3D measurement system can be realized by only 3 groups of calibration target images, and the calibration operation efficiency is higher than that of the basic matrix method, and (2) the accuracy of the multi-camera measurement system reaches 4 mm (3σ) in the range of 4000 mm×4000 mm×2000 mm, which is more accurate than traditional approaches with only 3 groups calibration images. The proposed method meets the requirements of accurate measurement of indoor moving target pose.
Design of laser parameter measurement system based on diffuse reflection imaging
Cheng Yilun, Tan Fengfu, He Feng, Hou Zaihong, Qin Laian, Wang Hao, Huang Zhigang, Wu Decheng
2022, 51(9): 20210921. doi: 10.3788/IRLA20210921
[Abstract](71) [FullText HTML] (16) [PDF 1415KB](32)
Accurate measurement of laser spot parameters after transmission in the atmosphere is a key technical means for studying the effects of laser atmospheric propagation and analyzing the performance of laser emission systems. The methods of measuring laser far-field parameters mainly include array detection method and camera imaging method. However, the current measurement and analysis of laser atmospheric transmission effect basically use array detection method. Because the detector array target detectors cannot be arranged uniformly and tightly due to the limitations of space physics and R&D costs, this will cause the distortion of the sampling spot and the far-field spot parameters cannot be accurately measured. Aiming at this problem, a set of laser parameter measurement system based on diffuse reflection imaging method is designed in combination with the high resolution of the camera. The minimum measurement resolution of the system is less than 0.39 mm, and the average deviation of the centroid position is 0.05mm, the uncertainty of the power from the measurement spot to the target is better than 10%. The system can effectively measure the tracking accuracy and target power of the laser emission system, and has accumulated a certain theoretical basis and experimental data for analyzing the laser atmospheric transmission effect and analyzing the performance of the laser emission system.
Calibration method and accuracy evaluation of visual target with double screen for straight pipe jacking machine
Huang Zhe, Yan Qingde, Li Qian, Cheng Erjing, Shen Xiaoling, Xu Yeqian
2022, 51(9): 20210933. doi: 10.3788/IRLA20210933
[Abstract](84) [FullText HTML] (19) [PDF 1619KB](24)
Aiming at the problem that it was difficult to calibrate the position and attitude relationship between the front and rear photosensitive imaging screens of visual target with dual-screen, a method for calibrating the position and attitude of the photosensitive imaging screen based on points-cloud was proposed. The front and rear photosensitive imaging screens were respectively divided into grid arrays of n rows and n columns. Combining the image 2D coordinates which were obtained in real time by industrial cameras and the spatial 3D coordinates which were measured by a total station to obtain the 2D-3D mapping relationship of each grid corner point on the photosensitive imaging screen, the coordinate point cloud data were acquired. Next, the 3D coordinates of the coordinate point cloud data are converted to the target coordinate frame according to the three common point coordinate frame transformation algorithm, which can determine the positional relationship between the camera and front/rear photosensitive imaging screen. And then the positional relationship between the front and rear photosensitive imaging screens was solved by the grid indexing method. In order to evaluate the accuracy of target attitude measurement, the static repeatability and the absolute measurement accuracy evaluation experiments were designed. The experimental results show that the static repeatability accuracy of the coordinates is 0.13 mm, the absolute accuracy of the coordinates is 0.93 mm, the static repeatability accuracy of the heading angle is 0.01°, and the absolute accuracy of the heading angle is 0.05°. Therefore, the calibration method can realize the accurate calibration of the pose of two spatial planes, which has the characteristics of simple operation and high precision, and can be used for calibration of visual target with double screen.
Research on time-stretched photon Doppler velocimetry
Lv Linjie, Wu Tengfei, Han Jibo, Zhao Lijie, Ma Pengmou, Chen Xiangmiao
2022, 51(9): 20210809. doi: 10.3788/IRLA20210809
[Abstract](57) [FullText HTML] (13) [PDF 1650KB](29)
In the transient high-speed velocity measurement scene, the target accelerates to several-tens of km/s in tens of ns. Therefore, the Doppler frequency shift can reach GHz or even hundreds of GHz. The velocity measurement range of photon Doppler velocimetry was limited by the current electrical digital to analog conversion technology. The time-stretched photon Doppler velocimetry used the time-stretched characteristic of femtosecond laser to reduce the signal frequency in the optical domain, which reduced the pressure of photoelectric signal detector and electrical digital-to-analog conversion device. An improved time-stretched photon Doppler velocimetry system was proposed in this paper. The femtosecond pulse was fully widened and spread over the whole time domain through the first stage dispersion fiber, in order to avoid the sampling interruption of velocity signal; In signal demodulation, error compensation algorithm was used to compensate the frequency shift signal, which reduced the system error caused by displacement and increased the effective recording time. Nanosecond laser was used to drive the aluminum film to produce high-speed flyer in the experiment, and the experimental results of the paper speed system were tested in the recording time of 1.2 µs. The repetition frequency 50 MHz femtosecond laser was used in the experiment. The first and second stage dispersion devices used 200 km and 100 km single-mode fiber, forming a scale factor of 2/3. In the end, the experiment showed that the Doppler shift signal of 3.6 GHz was reduced to 2.4 GHz, which was compared with the photon Doppler velocimetry system, and the experimental error was less than 5%. The system will be able to apply velocity measurement under dynamic high pressure technology loading flyer scene, and provides new measures for transient high-speed measurement area.
Directivity calibration and correction of bracket for star sensor
Li Yuanpeng, Guo Jiang
2022, 51(9): 20210875. doi: 10.3788/IRLA20210875
[Abstract](76) [FullText HTML] (16) [PDF 1827KB](31)
In order to ensure the high-precision pointing of bracket for star sensor after installation, a technical method for quantitative grind of bracket for star sensor was proposed. Firstly, we established the star sensor bracket’s coordinate system by constructing the virtual horizontal axis, then obtained the angle relationship between any two coordinate axes by the theodolite interactive measurement and sequential solving strategy. According to the results, we got the posture transformation matrix between star sensor bracket’s actual coordinate system and the space camera’s coordinate system. By the technical requirements of the star sensor bracket’s installing, we acquired the posture transformation matrix between the ideal star sensor bracket’s coordinate system and the space camera’s coordinate system. Then, we obtained the posture transformation matrix from the actual coordinate system to the ideal coordinate system by bridge of the camera coordinate system. According to this result, the corrective value of bracket for star sensor was accurately solved. The experimental research shows that this method can improve the star sensor bracket’s pointing accuracy from the initial 760″ to less than 10″ after two rounds of iteration, which proves effectiveness of the method. At the same time, directivity calibration and correction of bracket for star sensor can also guide the precise assembly and adjustment of other two components with spatial free angle relationship.
Quantitative analysis research of ChemCam-LIBS spectral data of Curiosity rover
Zhang Pengfei, Zhou Ting, Xia Daohua, Zhang Li
2022, 51(9): 20210962. doi: 10.3788/IRLA20210962
[Abstract](101) [FullText HTML] (27) [PDF 3018KB](31)
The traditional partial least squares method and support vector machine regression method were often difficult to obtain high accuracy and further optimization in predicting the element content of the ground standard sample of the rover corresponding to the spectrum. To solve the above problems, the three-channel folding of high-dimensional spectral information was carried out to eliminate its matrix effect in the research, and introduced the Residual Network structure (ResNet), which was good in the field of computer vision, to extract the spectral features and predict the corresponding principal component content. In this paper, the full connection layer in ResNET network structure was removed to prevent the sudden increase of model parameters, and the last Softmax classification sublayer of the network was changed into a linear rectification layer for prediction. At the same time, exponential learning rate attenuation and Dropout mechanism were added to make the model prediction results have higher accuracy and generalization ability. Compared with linear support vector machine regression (LinearSVR) and depth separable convolution network Xception, the prediction root mean square error of each main element content of the model decreases by 30% and 17% on average, respectively. The experimental results show that the regression model established by ResNet network shows good prediction characteristics when LIBS technology is used for principal element quantitative analysis of ChemCam spectral data.
Measurement technique research for the absorptivity of cryogenic radiometer absorbing cavity at the 4 K temperature
Yu Bing, Fan Jihong, Yuan Linguang, Li Yan, Guo Lei, Wang Xiao, Chu Junwei, Qin Yan, Sun Yunan, Zhang Deng, You Yue, Jin Weiqi
2022, 51(9): 20210984. doi: 10.3788/IRLA20210984
[Abstract](81) [FullText HTML] (17) [PDF 1292KB](28)
In order to realize measuring the absorptivity of cryogenic radiometer absorbing cavity at the 4 K temperature, a method of measuring the absorptivity with variable temperature is researched. By designing reflection monitoring components in front of the Brewster window of the cryogenic radiometer, and controlling the cryogenic radiometer to work in a vacuum environment of 10−6 Pa, then adjusting the refrigeration temperature of the cryogenic radiometer, the reflection signals of the cryogenic radiometer absorbing cavity are measured at 632.8 nm under room temperature and different temperature conditions. Combined with the measurement results of the reflectance at 632.8 nm of the cryogenic radiometer absorbing cavity at room temperature using the traditional integrating sphere method, the absorptivity of the cryogenic radiometer absorption cavity can accurately obtain under different temperature conditions through calculations. The experimental measuring the absorptivity of the absorbing cavity at room temperature and 4 K temperature, the absorptivity is 0.99976 and 0.999 71, respectively. The measurement uncertainty of the absorptivity of the cryogenic radiometer absorption cavity at the 4 K condition is evaluated, and the results obtained show that the relative expanded uncertainty is 0.005%(k=2).
Holographic microscopy detection method of microfluidic chip channel
Xu Jianan, Kong Ming, Liu Wei, Wang Daodang, Xie Zhongsi
2022, 51(9): 20210915. doi: 10.3788/IRLA20210915
[Abstract](54) [FullText HTML] (13) [PDF 2218KB](28)
Aiming at the detection requirements of the microfluidic chip channel and defect detection, a set of reflective image-plane digital holographic microscopic system based on the pre-amplified off-axis optical path was designed and constructed. In the digital holographic microscopy measurement, the phase distortion correction method of the low-spatial frequency objects whose lateral size occupies a relatively large field of view was discussed, and the two-step phase subtraction method was proposed to be more suitable for the phase distortion correction of this type of object. The phase distortion correction effects of two-step phase subtraction method, general polynomials surface fitting method and Zernike high-order polynomials surface fitting method were compared and analyzed through the experiment of a micro-step standard sample with a width of 55 μm and a height of 65 nm. The analysis results show that the relative error of the average height of the micro-step after the distortion is corrected by the two-step phase subtraction method is 1.1%, which is smaller than other methods and has a better distortion correction effect. In addition, the microfluidic chip with a channel width of 80 μm was used as the sample to detect the three-dimensional shape of the micro-channel, the fracture defect and defective defect on the surface of the channel. The quantitative results show that the width of the fracture defect is 14.1 μm and the depth is 431.7 nm. The defective defect has a width of 33.6 μm and a depth of 295.1 nm. The experimental results show the image-plane digital holographic microscopic system provides a new way for the rapid and non-destructive measurement of microfluidic chip microchannels and surface defects, which is of great significance for the quality evaluation of microfluidic experimental systems.
Research on ground detection model and test of optical reconnaissance satellite
Xing Hui, Zhang Yanxiu, Lei Ping, Ma Na, Wang Juanfeng, Kang Dayong
2022, 51(9): 20210978. doi: 10.3788/IRLA20210978
[Abstract](82) [FullText HTML] (18) [PDF 1470KB](36)
In the field of space optoelectronic countermeasures, the real-time on-orbit tracking of satellites by ground optoelectronic tracking equipment is a prerequisite for interference countermeasures, and optical reconnaissance satellites mostly operate in sun-synchronous orbits. Firstly, according to the optical reconnaissance satellite earth observation was apparent under vertical or lateral swing down more visual, and ground jamming equipment must be located within the optical reconnaissance satellite view characteristic, through independent mathematical deduction, the mathematical model of satellite and ground equipment location relationship between each other, including the ground photoelectric devices of optical reconnaissance satellite observation distance and the mathematical expression of observation angle; Secondly, according to the radiation scattering characteristics of the satellite and their solar panel, as well as the scattering transmission characteristics of the earth's atmospheric environment and terrain background in the visual band, the mathematical model of the scattering radiation transmission of the star and the observation path was derived, and the mathematical expression of the illuminance on the focal plane of photoelectric equipment which represent the target and the background respectively were obtained; Finally, based on the atmospheric scintillation characteristics of the scattered radiation of reconnaissance satellites, using probability statistical theory and engineering experience analysis, it was pointed out that the decisive factor affecting the detection probability was the change in the target background contrast caused by the atmospheric scintillation, based on this, a new detection probability model of the optical reconnaissance satellite by ground optoelectronic equipment was proposed. The actual test data verifies that the calculated results of the model in this paper are in good agreement with the actual measured data.
System-level calibration method for complex error coefficients of strapdown inertial navigation system
Wang Zichao, Fan Huiying, Xie Yuanping, Luo Hui, Yu Xudong
2022, 51(7): 20210499. doi: 10.3788/IRLA20210499
[Abstract](60) [FullText HTML] (18) [PDF 3205KB](20)
The establishment of a complex error model of strapdown inertial navigation system is researched, and a new system-level calibration method isproposed, which includes the inner level arm parameters of the accelerometer and temperature error coefficients. The method is based on the 45-dimensional Kalman filter to identify and estimate the error parameters, and the temperature change in the calibration process is controlled by a temperature control test chamber. Simulation experiments show that this method can simultaneously calibrate the constant drift, scale factor error, installation error of the laser gyroscope and accelerometer, as well as the inner level arm parameters and temperature coefficients of the accelerometer. The results of the navigation experiment show that when using the calibration parameters compensated for multiple error sources, the maximum positioning error of the navigation for 10 h is 0.6 n miles. The navigation accuracy is improved by 37.5% compared to that without compensation.
Full parameter rapid field calibration method for regular tetrahedral redundant inertial navigation
Zhai Xuerui, Ren Yuan, Wang Lifen, Zhu Ting, Wang Chen
2022, 51(7): 20210784. doi: 10.3788/IRLA20210784
[Abstract](55) [FullText HTML] (13) [PDF 1502KB](20)
Regular tetrahedral Redundant Inertial Navigation System (RINS) has the characteristics of high reliability and high precision, and error calibration is a necessary means to realize high-precision navigation solution. At present, the error calibration of regular tetrahedral RINS needs to be realized by using the high-precision turntable, which not only has high calibration cost and long calibration time, but also cannot calibrate full error parameters under the condition of insufficient hardware conditions such as external field. Address this issue, a rapid field calibration method for full error parameters of regular tetrahedral RINS without high-precision turntable was proposed. Firstly, the error model of regular tetrahedral RINS was established. Then, according to the relationship between the analytic coarse alignment attitude error matrix and the bias of regular tetrahedral RINS, a bias calibration method based on six positions was proposed. Then, a three-position rotation scheme was designed to calibrate the scale factor and installation error of the gyroscope. Finally, the six-position scheme of bias calibration was used to calibrate the scale factor and installation error of the accelerometer. Simulation and experiment show that this method can effectively calibrate full error parameters. In the 1h static base navigation experiment, the north positioning accuracy are improved from 61.065 5 km to 0.476 7 km, and the east positioning accuracy are improved from 161.202 7 km to 4.842 2 km.
Test method of the dynamic modulation transfer function in an indoor analog environment
Zhang Weiguang, Yu Xun, Han Feng, Zhang Faqiang, Wu Yinhua, Chen Yujiao
2022, 51(7): 20210756. doi: 10.3788/IRLA20210756
[Abstract](53) [FullText HTML] (15) [PDF 1956KB](24)
Aimed at the requirements of remote observation dynamic performance evaluation of photoelectric imaging systems such as vehicle visual intelligent perception and low altitude regional defense, an indoor simulated moving target system was developed. Based on the linear space shift invariant system model, the MTF measurement principles with ''three-bar target'' and ''four-bar target'' were analysed. A measurement method of the dynamic modulation transfer function (MTF) was proposed for an optoelectronic imaging system based on a variable frequency target. A design scheme of a variable frequency target was introduced, the solution method of MTF value was proposed, and the static and dynamic MTF comparative test experiments were conducted for ''three-bar target'' and variable frequency target. The experimental results show that compared with the "three bar target" measurement method, the proposed frequency conversion target dynamic MTF measurement method has a relative maximum deviation ratio of 1.9% for static MTF measurement and 2.8% for dynamic MTF measurement. The method can solve the MTF curve from one target image and has more advantages than ''knife edge method'', ''three-bar target'', ''four-bar target'' and other methods in the field of dynamic MTF measurement technology.
Research on lighting system based on LED current and temperature spectrum model
Li Jianfei, Zhou Xiaoming
2022, 51(7): 20210727. doi: 10.3788/IRLA20210727
[Abstract](41) [FullText HTML] (8) [PDF 1741KB](26)
Changes in current and temperature can affect the spectral distribution of the LED, which in turn affects the visual and non-visual parameters of the light source. In this paper, starting from the spectral model based on the distribution of photon energy levels in the LED chip luminescent material, the current and temperature model was established for the RGBY four-color LED. The R-square of the spectral fitting could reach 0.99. On this basis, the genetic algorithm (GA) was used to optimize the circadian rhythm factor and luminous efficiency with multiple objectives. When the illuminance was 300 lx, 8 sets of visual parameters (color rendering index and blue light hazard efficiency) and non-visual parameters ( circadian rhythm stimulus) were designed to verify the feasibility of this model. Then, the relationship between two non visual parameters and temperature was explored. The results show that the circadian rhythm factors increased with the increase of temperature, but the circadian rhythm stimulus decreased with the increase of temperature. The reason for this situation was that the two parameters were differently affected by the illuminance. After compensating the illuminance of the light source, it was found that the two non-visual parameters both increased with the increase of temperature, and the two showed a certain positive correlation. This research started from the perspective of the light source spectrum and provided a reference for the consideration of non-visual effects in the design of LED lighting sources.
Error detection system of photoelectric encoder based on optical continuous closed-loop
Li Kun, Ding Hongchang, Cao Guohua, Hou Han
2022, 51(7): 20210715. doi: 10.3788/IRLA20210715
[Abstract](54) [FullText HTML] (11) [PDF 1568KB](40)
In order to solve the problems of low accuracy, complex optical machine structure, and long detection cycle in the error detection of the photoelectric encoder, the optical small-angle measurement principle of an autocollimator and a polyhedral prism, and the continuous error detection method of the reciprocal rotation angle of the dual-axis turntable were combined to establish an error detection system for photoelectric encoder based on optical continuous closed-loop. By using the multi-body system theory and the relative pose matrix transformation method, a full error model of the dual-axis turntable was established, and the influence of the fixed error and variable error of the full error model on the system was analyzed. The detection system was calibrated with a calibrated autocollimator and a 23-sided polyhedral prism, and a high-precision photoelectric encoder was used to compare the detection accuracy with the system. The test results show that the rotation accuracy of the dual-axis had met the requirements of the numerical simulation calculations, the system detection accuracy had reached 0.38″, and the measurement uncertainty is 0.2″ (k=2). And for the encoder actually produced, the detection accuracy of the system is basically the same as the accuracy of the factory calibration. Which had been verified the feasibility of the optical continuous closed-loop system to achieve high precision and circumference continuous error detection.
High-precision 3D reconstruction method for topography measurement of complex mechanical parts
Wang Suqin, Chen Taiqin, Zhang Feng, Shi Min, Zhu Dengming
2022, 51(7): 20210730. doi: 10.3788/IRLA20210730
[Abstract](54) [FullText HTML] (10) [PDF 2020KB](31)
Accurate measurement of mechanical parts can provide a basis for parts processing and manufacturing, virtual simulation, defect detection and other applications. The binocular vision method based on fringe projection is widely used in the topography measurement of mechanical parts due to its high-precision characteristics. In this method, the quality of the absolute phase curve determines the final accuracy of the 3D reconstruction. Due to the influence of environmental noise, discontinuity of the scene, and complex surface structure of the parts, absolute phase curve often has a large number of noise points and varying degrees of deformation. In order to improve the reconstruction accuracy, a corresponding improvement method is proposed for the problems existing in the absolute phase curve. Aiming at the noise points far away from the phase curve that are difficult to remove, a region-by-region phase correction method is proposed. This method divides the phase curve of each row into several regions, and uses the median of the phase value in the region as the threshold to remove such noise points. For the deformed area of ​​the phase curve, the curve fitting method is introduced on the basis of the point primitive-based stereo matching method, and the disparity map obtained after the matching is refined, which can improve the poor matching result in the deformed area of the phase curve and improve the robustness and accuracy of the matching method. The method is used to reconstruct complex part FSW inverter, and the standard deviation can be reduced to within 0.1 mm. Experiments have proved that the reconstruction accuracy of this method is higher. For mechanical parts with complex surface structure, the proposed method can achieve accurate measurement.
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